Link chain belt

ABSTRACT

A chain belt formed of a plurality of pivotally connected preassembled parallel links. Each link includes a driving tooth protruding from one surface of the link midway between the pivotal axes of the link. The tooth is preferably formed so that its faces are a pair of intersecting, convex, cylindrical segments of like radii of curvature, the cylindrical axes of the segments being located such that the curvature of the faces insures that there if no scrubbing action where the belt is driven by a sprocket, the teeth of which are shaped to provide an inversely curved mating surface with the link teeth.

This application is a continuation of Ser. No. 228,154, filed Jan. 23,1981 now abandoned; which was a continuation of Ser. No. 013,165 filedFeb. 21, 1979 now abandoned; which was a continuation-in-part of Ser.No. 801,904 filed May 31, 1977 now abandoned.

This invention relates to articulated or linked belts, and particularlywith a novel belt comprising modules each comprising a plurality ofpreassembled link-like elements.

It has long been known that endless belts, in the form of a loop, can beused particularly as a conveyor, for the transmission of power, and forthe transmission of precise angular relationships, i.e. as a timingbelt. The simplest form is a loop of flat, flexible material driven byfrictional engagement, but such belts provide little, if any, intrinsicresistance to distortion under carrying load and tend to slip. Hence,their virtue is primarily in their cost, but they find littleapplication for precision power transmission, timing or conveyance. Forthe latter applications, the preferred belt is a chain drive. Precisionsteel roller chains and inverted tooth or silent chains are consideredprimarily power transmission and/or power timing chains, particularly ataverage to high speed conditions.

The well known silent or "inverted" tooth driving chains are generallycharacterized in that each driving link is usually provided with a pairof teeth extending outwardly from the link from approximately thepivotal axes of the latter, parallel to one another and perpendicularlyto the pitch line. While in theory these links have no sliding action inor out of the grooves of an associated sprocket wheel and are henceconsidered noiseless, in practice, the link teeth and sprocket teethengage one another with a scuffing or rubbing contact, known as"scrubbing", with attendant wear on the teeth. Additionally, in atypical operation of a silent chain, the contact between the driving anddriven faces of the chain teeth and sprocket teeth is substantiallyalong a line or a narrow area of the tooth faces extending parallel tothe rotational axis of the sprocket wheel. The driving pressure, beingthus concentrated over this very small area, typically requires that theteeth surfaces be specially hardened to reduce wear.

Prior art silent chains also claim to reduce the detrimental effect ofchordal action, i.e. the vibratory motion of the chain as it engages thesprocket wheel. This vibratory motion is manifest as a periodicacceleration and deceleration of the chain, and a rise and fall of thelinks of the latter with respect to its line of engagement with thesprocket wheel. Such chordal action, of course, is not present in afully flexible belt such as a rubber timing belt, for the latter simplyconforms at every point to the pitch circle of the sprocket wheel.However, for a chain formed of substantially rigid links which arepivotally joined to one another, flexible conformation to the pitchcircle of the sprocket wheel is impossible. Roller chains and the likeexhibit marked chordal action which limits high speed load carryingcapability and makes transfer of the load from the chain to a stationarycomb tangent to the sprocket wheel, particularly perilous for fragileitems being carried by the chain. In order to reduce the chordal actionof some current silent chains, the designers have provided ingenious pinand rocker-joints and involute chain teeth and sprocket teeth. When suchteeth engage one another, the contact point of the pin and rocker jointshifts upward and causes the pitch of the chain to elongate, reducingchordal action.

In U.S. Pat. No. 3,870,141 issued Mar. 11, 1975, there is disclosed achain link belt particularly useful as a conveyor, capable of carryingheavy loads and transmitting substantial power at fairly high speeds.The chain belt therein disclosed is particularly advantageous in that,being modular, it is very easily assembled and repaired.

The modular belt of U.S. Pat. No. 3,870,141 is generally formed of afirst plurality of link ends, each formed to circumscribe a pivotal holeand a second plurality of link ends, each also formed to circumscribe apivotal hole, the pivotal holes in each plurality of link ends beingrespectively aligned along a common axis. The axes of the pivot holes ofeach plurality of link ends are parallel with one another. Each link endof the first plurality is joined to a corresponding link end of thesecond plurality through at least one cross-rib which lies between andsubstantially parallel to the axes of the two pluralities of pivotalholes. The link ends are dimensioned and spaced apart by a distanceslightly greater than their respective widths. Thus, when the link endsof one module are nested or engaged with the link ends of another moduleby a common pivot pin extending through the pivotal holes in therespective link ends, the engagement of adjacent link ends tends tominimize the transmission of twisting shear to the pivot rod.Consequently, very advantageously the modules, chain belt and pivot pinsof U.S. Pat. No. 3,870,141 can be formed of polymeric materials, therebyminimizing costs, providing high strength with light weight and avoidinglubrication problems. This chain belt can withstand severe extremes ofprocessing temperatures, and highly corrosive environments such as areencountered frequently in laundries, food processing and othermanufacturing processes.

To drive the chain belt of U.S. Pat. No. 3,870,141, there is usuallyprovided a sprocket wheel with extending teeth arranged in staggeredrelation along the axis of rotation so that the teeth can engage asimilarly staggered array of openings formed by adjacent engagedmodules. These sprocket teeth bear against the portion of the link endwhich circumscribes the pivotal hole.

The present invention is directed toward a novel chain link having adriving tooth protruding therefrom intermediate pivot axes located atopposite ends of the link, the tooth having working surfaces of a uniqueconfiguration as hereinafter described. This novel chain link can beassembled to form a module for a chain belt generally of the typedescribed in U.S. Pat. No. 3,870,141 but particularly adapted to providevery precise power transmission and/or timing requirements. To this end,the present invention is also typically embodied in a modularlystructured chain belt in which each module is formed of a plurality oflinks each having a pair of link ends each formed to circumscriberespective pivotal holes, a number of links being arranged so that afirst set of such holes in first plurality of such link ends are alignedalong a common first linear axis, and a second set of such holes in asecond plurality of such link ends are aligned along a second commonlinear axis, the first and second axes being parallel to one another. Inthe module formed of links of the present invention, each of the linkends of the first plurality is joined with the corresponding ones oflink ends of the second plurality through an intermediate portion. Inembodiments where the links are integrally joined to one another, theintermediate portion extend substantially parallel to the first andsecond axes. Appended to, and preferably formed integrally with eachlink is a single driving tooth which protrudes intermediate the firstand second axes generally in a first direction perpendicular to a planecommon to those axes. The tooth is preferably formed with its workingsurfaces as a like pair of plano-convex surfaces each being typically asubstantially cylindrical segment of like radius of curvature, therespective cylindrical axis of each such segment being between the firstand second axes through the pivotal holes. The term "working surface" isintended to refer to that surface of a tooth adapted to engage a drivingelement such as a sprocket or an element to be driven, as the case maybe.

A particular object of the present invention is to provide a link of thetype described which, in conjunction with a sprocket wheel ofappropriate configuration, exhibits substantially no scrubbing action.Another object of the present invention is to provide a link of the typedescribed, a plurality of which when formed into a hinged, endless beltused in conjunction with an appropriate sprocket wheel, exhibitsremarkably small chordal action.

Other objects of the invention will in part be obvious and will in partappear hereinafter. The invention accordingly comprises the apparatuspossessing the construction, combination of elements, and arrangement ofparts which are exemplified in the following detailed disclosure, andthe scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the presentinvention, reference should be had to the following detailed descriptiontaken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a typical link formed according to theprinciples of the present invention;

FIG. 2 is an enlarged view of a section taken along the line 2--2 ofFIG. 1;

FIG. 3 is a perspective view of a module formed of links of FIG. 1;

FIG. 3A is a top plan view of the module of FIG. 3;

FIG. 4 is a section taken along the line 4--4 of FIG. 3A;

FIG. 5 is a side view of a portion of a linked belt formed of themodules of FIG. 3, in engagement with a driving sprocket wheel, shownonly in fragment;

FIG. 6 is a front elevation view of a modification of the module of FIG.3, particularly adapted for use with a V-sheave sprocket drive;

FIG. 7 is a front elevation of the mirror form of the module of FIG. 6;

FIG. 8 is a fragmentary showing of a V-sheave sprocket drive only takenalong the line 8--8 of FIG. 5;

FIG. 9 is an end view of yet another modification of a link formedaccording to the principles of the present invention;

FIG. 10 is an end view of yet another modification of a link formedaccording to the principles of the present invention;

FIG. 11 is an end view of an extreme form of a link formed according tothe principles of the present invention;

FIG. 12 is an end view of a double-toothed version of a link formedaccording to the principles of the present invention;

FIG. 13A is a diagram showing the relation of the teeth of links of thepresent invention to a sprocket wheel formed according to the presentinvention;

FIG. 13B is a simplified version of the diagram of FIG. 13A showing thedisplacement of a link tooth and sprocket wheel through an angle of 15°relative to the sprocket center line;

FIG. 13C is a diagram similar to FIG. 13A but in which the link toothsurfaces are not formed within the teachings of the present invention;

FIG. 13D is a diagram similar to FIG. 13A but in which the centers ofcurvature of the tooth faces are coincident with the pivotal axes of thelink;

FIG. 14 is a side view of a portion of a belt formed from the modules ofFIG. 3 arranged to serpentine through a pair of counter-rotating drivingsprockets;

FIG. 15 is an end view of yet another modification of a link of thepresent invention.

FIG. 16 is a diagram according to the present invention useful inanalyzing the chordal action of the belt and sprocket wheel of thepresent invention;

FIG. 17 is a graph showing the chordal variations in velocity using atwelve tooth sprocket wheel in the present invention;

FIG. 18 is a perspective view of another form of link embodying theprinciples of the present invention;

FIG. 18A is an end view of the link of FIG. 18; and

FIG. 19 is a top plan view of a fragment link belt formed of links ofFIG. 18.

In FIG. 1 there is shown a typical link of the present inventiondesignated generally at reference numeral 21 formed as an elongatedelement having a pair of parallel side surfaces (only one of which isshown). A first link section or end 22 is formed to circumscribe a pivothole 24 having a central pivotal axis A normal to the axis of elongationof link 21, the opposite link section or end 26 being similarly formedto circumscribe another pivotal hole 28 having a central pivotal axis Bparallel to axis A. Appended to and preferably formed integrally withlink 21 is included at least one driving tooth 32 which protrudesgenerally in a direction perpendicular to the common plane through thefirst and second pivotal axes A and B and intermediate, preferablymidway, between the latter. The side surfaces of tooth 32 are, in thisembodiment, coextensive with and coplanar with the corresponding sidesurfaces (such as surface 23) of link 21. As shown particularly in FIG.2, the faces of tooth 32 are formed preferably of a pair ofplano-convex, e.g. cylindrical surfaces 34 and 35 which intersect oneanother. Surfaces 34 and 35 are shown as substantially right-angledcylindrical segments having like radii of curvature, the cylindricalaxes or axes of rotation P₁ and P₂ respectively of surfaces 34 and 35being parallel to one another and disposed between and in a planeparallel to or coplanar with first and second pivotal axes A and B. Forexample, as shown in FIG. 2, surface 34 has a radius of curvature R₁,the origin or center of curvature lying at axis P₁, here shown disposedbetween and intersecting pitch line L through pivotal axes A and B ofholes 24 and 28. Similarly, surface 35 has a radius of curvature whichis centered as axis P₂ similarly intersecting line L, and lies betweenthe centers of pivotal axes A and B of holes 24 and 28. It will be seentherefore that the intersection of surfaces 34 and 35 lies along a lineI (shown as a point) parallel to and equidistant from the first andsecond axes A and B, so that tooth 32 is preferably bilaterallysymmetrical about line I.

The configuration of surfaces 34 and 35 of tooth 32 shown in FIG. 2 arenot only plano-convex, but the locations of the axes of curvaturethereof are of great importance. Specifically, axis P₂ is at somedistance d from axis A and axis P₁ is the same distance from axis B,i.e. they are equidistant from the nearest respective pivotal axis. AxesP₁ and P₂ are in a common plane parallel to or coplanar with the commonplane of axes A and B. For any point X on surface 34, there is a tangentT which, of course, is a perpendicular to R₁ the radius of curvature ofsurface 34 to point X. The location of axis P₁ must then be such that anangle θ between tangent T and line D, which extends from point Xperpendicularly to the pivotal axis (here axis B) nearest to axis P₁, isnot more than 90° when observed looking into the convex surface of theopposite face (here surface 35). Because as noted, the tooth isbilaterally symmetrical, this constraint applies also to the location ofaxis P₂ with respect to axis A and any point on surface 35. If angle θ,hereinafter in this specification and claims referred to as the tangentangle, is 90° or less for each tooth surface, then as discussedhereinafter, the tooth will seat in a corresponding groove of a sprocketwheel without scrubbing. Not only does the structure of tooth 32 providea non-scrub action, but when used with appropriate sprocket wheels,typically a minimum of twelve or more grooves matched to tooth 32,chordal action is reduced very substantially over prior roller chainstructures formed of links 21, as will be described hereinafter.

Reference is now made to FIGS. 3 and 3A inclusive wherein there isillustrated one embodiment of a chain link module incorporating theprinciples of the present invention. This module, generally designatedat 20, is designed to be formed as an integral unit typically, but notnecessarily of polymeric material by any of a number of conventionalmolding processes. The polymer used is preferably a glass-reinforcedpolypropylene, but many other materials can be used as well. Module 20comprises a multiplicity of elongated, parallel, spaced-apart, links 21which for the sake of convenience in illustration and exposition, areshown to be five in number, although it is to be understood that themodule can and frequently does, comprise a substantially greater orlesser number of such links 21. All of links 21 have substantially thesame length and width, and thus the length dimension of module 20 isdetermined by the length of the individual links while the width ofmodule 20 is determined by the number of links, their width and thespacing therebetween. In the embodiment shown in FIGS. 3 and 3A, all oflinks 21 are preferably rigidly joined together and held insubstantially parallel relation by an integrally formed intermediatesection 30, thus forming a rigid, open or slotted structure in which theparallel link ends alternate with slots 31. Alternatively, module 20 canbe formed of a plurality of links 21 and requisite spacers to provideslots 31, all held together mechanically as by adhesive or the like. Thelength of each slot is at least equal to twice the distance between thecenter of a hole such as 24 and the distal extremity of associated link22, thereby providing sufficient space into which a corresponding linkend of another like module can fit so that the respective holes in thefitted link ends are registered with coaxial pivot holes. Link ends 22and 26 are held spaced apart by adjacent surfaces by a distance justslightly greater (e.g. 0.003 inches or less) than the width of the linkends so that the link ends of each module may fit snugly but movablybetween the link ends of an adjacent module with parallel facingsurfaces in contact with one another.

Thus, as shown particularly in FIG. 3A, the module includes a firstplurality of pivot holes 24 which are all aligned coaxially along firstlinear pivotal axis "A" and a second plurality of pivotal holes 28 whichare similarly coaxially aligned along second linear pivotal axis "B",the first and second linear axes A and B being parallel to one another.The respective pluralities of aligned pivot holes are intended toreceive pivot rods or pins which are adapted to pivotally connect module20 with like modules end-to-end while laterally aligning the adjacentmodules. In the embodiment shown wherein module 20 is formed ofintegrally molded together links 21 and intermediate section 30, theface width of each tooth 32 is selected so as to form an integral unittooth which extends across the entire width of module 20, i.e. from oneend element 21 to the other end element 21. This form of tooth 32 lendsitself to ready molding in the formation of the modules and provides alarge and stable driving surface, as will be described later herein.However, unit tooth 32 can be molded to be of somewhat different widththan the width of module 20 between end elements 21 and can be formed,instead, simply as a plurality of individual, arranged teeth 32corresponding to the respective links.

The modules, subject to the above-described constraints on the geometryof the working surfaces of tooth 32, may take a number of slightlydifferent configurations. Some examples of alternative configurationsare shown in FIGS. 9, 10 and 25 wherein respectively the module of FIG.9 includes a dished portion or concavity 36 in the portion thereofopposite tooth 32, concavity 36 being in the form of a trough having itslong axis substantially parallel to linear axes And B through holes 24and 28. A linked belt formed of the modules of FIG. 9 would have acorrugated upper surface with the corrugations extending in a directionsubstantially perpendicular to the direction of belt travel, and forexample, would provide either a high speed drainage surface for somearticles to be conveyed thereon or a surface capable of engaging andcarrying various articles of appropriate size. It will be seen thattooth 32 of the module of FIG. 9 is formed of a pair of surfaces 34 and35 in substantially the same manner as the tooth shown in FIGS. 1, 3 and4. However, it will also be seen that the apex of tooth 32 in FIG. 9however has been provided with a separate radius of curvature so as toblunt the apex somewhat.

Alternatively, as shown in FIG. 10, faces 34 and 35 are cylindricalsegments and the surface of the module opposite tooth 32 is maintainedas a substantially flat surface (at least along the link-like elements21). However, the apex of tooth 323 has been truncated as at 37 so as toprovide a relief space with regard to a sprocket groove, or so that theteeth of the sprocket can be shortened if desired.

If a modification of the module of FIG. 10 shown in FIG. 15, tooth 32 isfaced with substantially flat surfaces 34A and 35A which can be chordsor part of chords of the cylindrical segments constituting faces 34 and35 of the device of FIG. 10. Surfaces 34A and 35A need not be flat butcan assume a curvature lying between the cylindrical curvature of faces34 and 35 of FIG. 10 and a plane forming a chord to that cylindricalcurvature so long as the tangent angle is not more than 90° as noted.

A plurality of modules 20 are assembled in end-to-end (and if desiredside-to-side) relation to form belt 36 (shown in fragment) whenconnected by pivot rods 38 as shown in FIG. 5. Holes 24 of one moduleand holes 28 of the next module are joined by pivot rod 38 to create apin-and-bushing type of joint. It will be appreciated that intermediatesection 30 as reinforced by its connection with tooth 32 functions tosupport elements 21 against lateral forces tending to separate the linksas well as one twisting or bending forces on the modules which wouldtend to shear pivot pins 38. To drive belt 36 formed by linking aplurality of modules 20 together with pins 38, there is provided asimple sprocket wheel 40 shown only in fragment, sprocket wheel having aplurality of radial teeth 42. Each groove defined by surfaces 44 and 45lying between adjacent teeth 42 are shaped to mate, at least in majorpart, with the corresponding surfaces 34 and 35 of teeth 32, i.e.surfaces 44 and 45 are cylindrical segments which are the inverse ofsurfaces 34 and 35 respectively, in that the former surfaces are concavewhere the latter surfaces are convex. It will be appreciated that when apair of modules 20 are coupled to one another by pivot pin 38 becausethe modules are staggered the width of the combined modules is greaterthan the width of a single module by at least a width of one link-likeelement 21. The axial width of the driving teeth 42 on sprocket wheel 40should therefore preferably have a width at least equal to or greaterthan the width of the coupled modules.

As noted earlier, the curves employed in shaping tooth 32 and thematching sprocket serve to insure that the tooth faces cannot rub orabrade the sprocket surface during entry to exit, i.e. obviatesscrubbing action, thereby minimizing wear and permitting high speedoperation.

This can be demonstrated by a numerical analysis of the relationshipbetween the position of arc centers for tooth profile relative to linkpivot points, and the scrubbing action of belt links on the drivingsprocket. Assume for example that conveyor belt 36 approaches thedriving sprocket wheel 40 and is supported upon carrying ways so thatthe centers of the pivot rods 38 connecting the individual conveyor beltlinks 20 approach wheel 40 on a horizontal line. When any pivot rodcenter reaches the vertical center line of the driving sprocket, it isfully supported by the sprocket. Referring particularly to FIG. 13A (inwhich only teeth 32 are shown as part of a link, and teeth 32 are intruncated form as in FIG. 15) it can be seen that pivot rod 38A is onthe vertical center line CL so that tooth 32A is fully seated in anappropriate groove on sprocket wheel 40, while tooth 32B is approachingwheel 40 and quite separate from the latter. As the center of pivot rod38A is carried around the sprocket wheel, it follows a circular path P.Therefore, the center of any pivot rod approaches the driving sprocketon a straight horizontal line L to the sprocket vertical center line CL,then follows a circular path P at the pitch radius R around the sprocketwheel.

The vertical height of the center of pivot rod 38A above the sprocketcenter is equal to the pitch radius R. Radius R is determined by theconveyor belt pitch pt of 1.1811 inches (30 mm) and the number of teethin the sprocket. For a 12-tooth sprocket, pitch radius R is(1.1811/2)/sin 15°=2.2817 inches. Thus distance R is 1.93185 times thepitch. Conversely, the pitch is 0.5176R for a 12-tooth sprocket. Theradius to the profile of the conveyor belt link was chosen as 0.748inches.

The distance from the sprocket center to the line pt between centers 38Aand 38B in FIG. 13A is 2.2817 cos 15°=2.2040 inches. With these factorsknown, it is possible to calculate the position of a pivot rod centerfor and sprocket position or any point along a straight line connectingthe pivot rod centers of a conveyor belt link. The reason for wanting tolocate the position of these points is that the centers of the arcswhich define the profiles of conveyor belt link which engage thesprocket lie along this line. For exemplary purposes, the centers forthe arcs which define the belt tooth faces or profiles have beenselected at a distance d which is one-quarter of a pitch in from thepivot rod centers or pivot points, so that the tangent angle as noted isless than 90°.

Next, consider the position shown in FIG. 13B, where the pivot point 38Ahas advanced 15° with respect to FIG. 13A beyond the vertical centerline. The belt link center line pt connecting the pivot points made anangle β with the horizontal line L. The sine of the angle β is1.93185(1=cosα), where α is the angle the line G connecting pivot point38A and the sprocket center makes with the vertical center line CL. Forα=15°, β=arc sin 1.93185(1-cos 15°)=3.774°. At a distance of one-quarterthe pitch left of pivot point 38A, i.e. at point H, the verticaldistance below horizontal line L is 0.75(1.1811) sin 3.774°=0.0583inches. Point H is the center of the radius to the tooth face orprofile. The vertical distance to point J, the center of the radius tothe sprocket tooth face, from horizontal line L is 2.2817-2.2040 or0.0777 inches. This is 0.0194 inches below point H as as shown, tooth32B will not rub on the sprocket.

Next, consider the position shown in FIG. 13C, again with the angle αequal to 15°. This time, the centers of curvature for the faces of tooth32B are shown located one-quarter pitch outside the pivot points so thatthe tangent angle is greater than 90°. Again, β is 3.774° since α isstill 15°. Point H is 1.25(1.1811) sin 3.774°=0.0972 inches below thehorizontal line. Point J is 2.2040 inches above the sprocket center or0.0777 inches below the horizontal line. Therefore, point J is 0.0195inches above point H. For this case, the link tooth face would betheoretically below the sprocket tooth face. Since this cannot happenpractically, the link tooth face will rub on the sprocket tooth face itdrops into its seat (while the sprocket rotates 30°), and pivot point38C will be lifted above horizontal line L.

As a fourth and final case, consider the position shown in FIG. 13D.Again, the angle α is chosen as 15°, but this time the centers for thebelt link tooth faces are selected in the unique positions of exactly atthe pivot points, and the tangent angle equals 90°. The distance ofpoint H would be 1.000(1.1811) sin 3.774°=0.0777 inches below thehorizontal line. Point J would be 2.2817-2.2040 or 0.0777 inches belowthe horizontal line. Therefore, point J and H would be coincidental, andthe link tooth face and the sprocket tooth face would be coincidental.Theoretically, they would be in contact as the belt link dropped intoits sprocket seat, but with no rubbing pressure between the two.

As earlier noted, only the pivot points of the belt lie on the pitchcircle as they travel around the sprocket wheel, and lines connectingthe pivot points fall below the pitch circle. The links approaching thedriving sprocket, therefore, have a variable velocity characteristic ofthe chordal effect. The belt made with links as hereinbefore describedcan be analyzed for chordal effect by determining the distance traveledby a pivot point as it approaches the driving sprocket for a small angleof sprocket rotation.

A twelve-tooth sprocket with a conveyor belt pitch of 1.1811 inches (30mm) will be assumed for this analysis as shown in FIG. 16 because, aswell known, sprockets with more teeth will exhibit less chordal actionproportionately. The pitch radius R is again assumed to be(1.1811/2)/sin 15°=2.2817 inches, i.e. 1.93185 times the pitch. Theangle β is the angle between an extension of the horizontal line L uponwhich the pivot points approach and a line pt connecting pivot points38A and 38B. The sine of this angle is 1.93185 (1-cos α) where α is theangle line G through the sprocket center and pivot point 38B makes withthe sprocket vertical center line CL. The horizontal distance from thevertical center line CL to the pivot point 38B is R sin α. Thehorizontal distance between pivot points 38B and 38A is λ cos β.Therefore, pivot point 38A is shown at λ cos β--R sin α to the left ofthe sprocket vertical center line CL.

To determine the velocity variation, the distance from pivot point 38Ato the sprocket vertical center line was calculated for every twodegrees of sprocket rotation and a plot of the velocity variation forabout 30° of driving sprocket rotation is shown in FIG. 17.

With this analysis in hand, it is seen that the conveyor belt action andvelocity variation are considerably different from that of a rollerchain running on a sprocket with the same number of teeth. For example,a similarly dimensioned roller chain would rise and fall approaching atwelve-tooth sprocket, and the velocity variation from chordal actionwould be about 7.2 percent. The present invention exhibits animprovement of about 700% over such a chain.

In one particularly desireable form of the present invention as shown inFIGS. 6 and 7, module 20 is formed with at least one edge or end element21 designated as edge guide 43 having a width which is smaller at ornear tooth 32 (the bottom portion as shown) than at the top (as shown)so that the edge of end link or element 21 is tapered or beveled throughan angle α as shown in FIG. 6. A belt can then be formed of modules suchas is shown in FIG. 6, by providing that each alternative module issimply a reversed form of the module of FIG. 6 so that edge guide 43alternates from left to right along the belt. When this belt isassembled by joining the alternately reversed modules with pivot pins38, the cross section of the belt will have a V-shaped configuration,thus providing a link belt which also then possess attributes ofV-belts. To drive such a link belt with a V-shaped configuration,sprocket wheel 40 of FIG. 5 can have the configuration of a pitchedchain sheave such as is shown in FIG. 8 where the central hub orsprocket with teeth 42 is disposed between a pair of circular flangesshaped as shallow conical discs 44. The conical angle of discs 44 shouldbe matched to the taper angle, α, of the module shown in FIG. 6 to gainthe advantages of V-belts.

The links of the present invention, such as are shown in FIG. 1 can alsobe assembled to form a belt in which only every other (or third, fourth,etc.) pivotally coupled link (or module as the case may be) bears atooth 32 particularly when the links or modules are very small. Further,one can assemble a belt in which teeth 32 do not necessarily allprotrude in the same direction radially either inwardly or outwardlywith respect to the endless loop formed by the belt. For example, asshown in FIG. 14, the links or modules formed therefrom may be assembledso that teeth 32 protrude radially (with respect to the loop formed bythe belt) in alternately opposite directions. When used with a pair ofcounter-rotating driving sprockets 40A and 40B (similar to sprocket 40of FIG. 5) the belt of FIG. 11 can be driven along a tortuous orserpentine path with substantially no slippage or power loss andtherefore provides a very precise timing belt. Alternatively, one canemploy a double-tooth link such as is shown in FIG. 12 which includes asecond tooth 32A extending on the opposite side of the module from tooth32 and formed of two cylindrical surfaces centered on axes denoted as P₂and P₁ or even other points.

As shown in FIG. 11, when the pitch of a link (i.e. the distance betweenaxes A and B) is sufficiently large in relation to the thickness orheight of the link, one can generate both surfaces 34 and 35 about asingle axis shown as point P₃ lying equidistant between axes A and B. Itwill be apparent that the closer to the midpoint between A and B oneplaces the axes of revolution of surfaces 34 and 35, the shallower willbecome tooth 32 (the extreme case being the circular segment shown astooth 32 in FIG. 11), but the tooth separation (i.e. the spacing betweentooth and sprocket surfaces per angular degree of movement of the linkabout either pivotal axis A or B) is maximized.

Another variation of the link of the present invention is shown in FIGS.18 and 18A, wherein the link is formed, much as in FIG. 1, as anelongated element 121 having a first link end 122 formed to circumscribea pivot hole 124 having a central pivotal axis A normal to the axis ofelongation of the link, the opposite link end 126 being similarly formedto circumscribe another pivotal hole 128 about pivotal axis B parallelto axis A.

Appended to link 21 and extending therefrom in a direction perpendicularto the common plane of axis A and B and intermediate the latter isdriving tooth 132. The latter has a first side parallel to, coextensivewith and coplanar with side surface 133 of link 121 (i.e. surface 133being perpendicular to both axes A and B) as shown particularly in FIG.18A, in the same manner as in the embodiment of FIG. 1, each sidesurface of the tooth 32 being coplanar with the corresponding parallelside surface of the link. In the link of FIG. 18 and 18A, tooth 132however is slightly more than twice as wide as the width of the otherportion of the link (i.e. the distance between side surface 133 andopposite side surface 131) so that, in effect tooth 132 includes aportion 138 which extends outwardly from surface 136. Working surfaces134 and 135 of link 121 (corresponding to working surfaces 34 and 35 oflink 21 in FIG. 1) are formed exactly as heretofore described inconnection with link 21 of FIG. 1.

Although portion 138 is shown as a solid protrusion bounded by workingsurfaces 134 and 135 and having a flat top or upper surface 140 lying ina plane parallel to but displaced from the common plane of axes A and B,it will be appreciated that if one wishes to conserve material andreduce link weight, portion 138 can be formed as a hollow protrusion.Typically, in this latter case, portion 138 would be bounded by surfaces134 and 135, but upper surface 140 would be concave toward the toothapex or even molded with inner walls approximately paralleling workingsurfaces 134 and 135.

As will be seen from the fragment shown of the belt of FIG. 19, linkssuch as link 121 A formed of one "handedness" (for example, with portion138 extending out from surface 131 as described) can be formed into aside-by-side module and combined with a module made of side-by-sidelinks of opposite "handedness" (i.e. links such as 121B wherein portion138 extends from surface 133 instead) to provide a belt in which no edgediscontinuities or gaps are formed as would be the case using modulessuch as those of FIG. 3A. In effect, the design of tooth 132 as beingslightly more than twice the width of the upper portion of the link,provides an automatic spacer between side-by-side assembled links.

Since certain changes may be made in the above apparatus withoutdeparting from the scope of the invention wherein involved, it isintended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted in an illustrative and notin a limiting sense.

What is claimed is:
 1. A linked belt and sprocket assembly comprising:aplurality of identical linked modules, each having a plurality of linksof the same length and width and sufficiently rigid to resist bending inthe plane of an associated sprocket wheel, each module having a firstplurality of link ends of substantially identical width, and a secondplurality of link ends of substantially identical width, each link endcircumscribing a pivotal hole, said holes of said first plurality beingarranged coaxially along a first pivotal axis, said holes of said secondplurality being arranged coaxially along a second pivotal axis parallelto said first axis; said link ends having no driving engagement with anassociated sprocket wheel; each of said modules having at least onedriving tooth integral with and protruding therefrom substantiallynormal to the pitch line between said pivotal axes and intermediate thelatter; said tooth having a pair of working surfaces, each of theworking surfaces having a shape in the range between and including thatof a cylindrical segment and a chord of said segment; the .[.axis.]..Iadd.axes .Iaddend.of .[.each.]. .Iadd.the .Iaddend.working.[.surface.]. .Iadd.surfaces .Iaddend.being .Iadd.spaced apart and.Iaddend.parallel with the pivotal axes of the link and positionedintermediate the pivotal axes .[.or coincident with the pivotal axisfurthest from that surface.].; the pair of working surfaces being partof a pair of intersecting loci; the shape of each of the workingsurfaces being such that the tangent angle of each such surface is notmore than 90°; one of said pluralities of link ends of each said modulebeing engaged between one of said pluralities of link ends of anadjacent module except for the individual link ends positioned at theextreme sides of said belt; means extending through said holes pivotallyconnecting said modules at engaged link ends; a toothed sprocket wheelhaving recesses between adjacent teeth thereof, each of said recessesincluding a pair of facing surfaces of shape corresponding to the pairof working surfaces of said driving tooth; and only the teeth of saidconnected links being in driving engagement with the recesses of saidsprocket wheel, the engaged linked belt and sprocket wheel exhibitingminimal scrubbing action and chordal action.
 2. A linked belt assemblyas defined in claim 1 wherein said working surfaces are like surfaceswith substantially identical radii of curvature.
 3. A linked beltassembly as defined in claim 1 wherein said tooth is blunted, adjacentsaid line of intersection, by a surface formed as a cylindrical segmenthaving its axis on said line.
 4. A linked belt assembly as defined inclaim 1 wherein said tooth is truncated adjacent said line ofintersection.
 5. A linked belt assembly as defined in claim 1 whereinthe radii of curvature of said surfaces are centered at a commoncylindrical axis.
 6. A linked belt assembly as defined in claim 1wherein said link ends and tooth are of the same width.
 7. A linked beltassembly as defined in claim 1 wherein said working surfaces and facingsurfaces are cylindrical segments of substantially like radius ofcurvature.
 8. A linked belt assembly as defined in claim 7 wherein theaxes of said cylindrical segments lies substantially in plane common tosaid first and second axes.
 9. A linked belt assembly as defined inclaim 1 wherein said working surfaces are curved and said facingsurfaces are curved and inverse to the curved working surfaces.
 10. Alinked belt and sprocket assembly as defined in claim 1 wherein each ofthe modules includes:a tapered side which tapers toward the drivingtooth such that in cross-section the module is smaller near the drivingtooth, the taper having an angular configuration to mate with acorresponding V-shaped wheel; said modules being pivotally connected atengaged link ends, the tapered side of each module being opposite to thetapered side of adjacent modules to provide an average cross-section ofsaid belt having a V-shaped configuration to mate with a correspondingV-shaped wheel.
 11. A linked belt and sprocket assembly as defined inclaim 10 wherein the sprocket wheel includes a pair of circular flangeshaving confronting tapers conforming to the V-shaped cross-section ofthe pivotally connected modules.
 12. A linked belt and sprocket assemblycomprising:a plurality of identical linked modules interconnected inend-to-end relation to form a belt, each module including: a pluralityof link members of identical shape; each member having a flattenedelliptical portion with first and second ends and a tooth portionprojecting outward from said elliptical portion; said ends each havingfirst and second pivot holes therethrough and defining first and secondpivot axes axially through said pivot holes; said first and second pivotaxes defining a pitch plane and said tooth of each link member beingsymmetrically disposed about a plane orthogonal to the pitch plane andparallel to and bisecting the pitch axes; means extending throughrespective first and second pivot holes of adjacent modules to secureadjacent modules one to the other and to provide for pivotable rotationof adjacent link modules, said projecting tooth of each module havingfirst and second working surfaces each symmetrically disposed on arespective side of said orthogonal plane and which intersect at a lineparallel to the pivot axes in said orthogonal plane; each workingsurface having a shape in the range between a cylindrical segment and achord of a cylindrical segment having a center located .[.at thefarthest pivot axis or.]. between .[.that.]. .Iadd.the farthest pivot.Iaddend.axis and the orthogonal plane; a toothed sprocket wheel havingrecesses between adjacent teeth thereof, each of said recesses includinga pair of facing surfaces of shape corresponding to the pair of workingsurfaces of said projecting tooth; only the teeth of said link membersof respective modules being in driving engagement with the recesses ofsaid sprocket wheel, the engaged link belt and sprocket wheel exhibitingminimal scrubbing action and chordal action; and said teeth of saidsprocket wheel engaging said link modules and being radially alignedwith respective pivot axes during sprocket wheel and link moduleengagement.
 13. The assembly of claim 12 wherein said tooth is bluntedadjacent said line of intersection by a surface formed by a cylindricalsegment having its axis on said line.
 14. The assembly of claim 12wherein said tooth is truncated adjacent said line of intersection. 15.The assembly of claim 12 wherein said link ends and tooth are of thesame width.
 16. The assembly of claim 12 wherein the projecting teeth ofadjacent link members are joined with material of cross-sectionidentical to the tooth member to form a solid tooth member extending thewidth of the link module.
 17. A belt and sprocket assembly comprising aplurality of identical linked modules of unitary constructioninterconnected in end-to-end relation to form a belt, each moduleincluding:a plurality of link members of identical shape; each memberhaving a flattened elliptical portion with first and second ends and atooth portion projecting outward from said elliptical portion; said endseach having first and second pivot holes therethrough and defining firstand second pivot axes axially through said pivot holes; a plurality ofintermediate rigid members integral with said link members for spacingsaid plurality of link members equally one from the other to coaxiallyalign first and second pivot axes of respective link members and permitinterpositioning of the first link member ends of one link module withinspaces between second link member ends of an adjacent link module; saidfirst and second pivot axes defining a pitch plane and said tooth ofeach link member being symmetrically disposed about a plane orthogonalto the pitch plane and parallel to and bisecting the pitch axes; meansextending through respective first and second pivot holes of adjacentmodules to secure adjacent modules one to the other and to provide forpivotable rotation of adjacent link modules; said projecting tooth ofeach module having first and second working surfaces, each symmetricallydisposed on a respective side of said orthogonal plane, said surfacesintersecting at a line parallel to the pivot axes in said orthogonalplane; each working surface having a shape in the form of a cylindricalsegment, the segment having a center located .[.at the farthest pivotaxis or.]. between .[.that .Iadd.the farthest pivot .Iaddend.axis andthe orthogonal plane; a toothed sprocket wheel having recesses betweenadjacent teeth thereof, each of said recesses including a pair of facingsurfaces of shape corresponding to the pair of working surfaces of saidprojecting tooth; only the teeth of said link members of respectivemodules being in driving engagements with the recesses of said sprocketwheel, the engaged link belt and sprocket wheel exhibiting minimalscrubbing action and chordal action upon engagement of said belt withsaid wheel; and said teeth of said sprocket wheel engaging said linkmodules and being radially aligned with respective pivot axes of saidlink modules upon sprocket wheel and link module engagement.
 18. Theassembly of claim 17 wherein said tooth is blunted adjacent said line ofintersection by a surface formed by a cylindrical segment having itsaxis on said line.
 19. The assembly of claim 17 wherein said tooth istruncated adjacent said line of intersection.
 20. The assembly of claim17 wherein said link ends and tooth are of the same width.
 21. Theassembly of claim 17 wherein the projecting teeth of adjacent linkmembers are joined with material of cross-section identical to the toothmember to form a solid tooth member extending the width of the linkmodule.
 22. The assembly of claim 17 wherein said working surfaces arecurved and said facing surfaces are curved and inverse to the curvedworking surfaces to confront said working surfaces upon link module andsprocket wheel engagement.
 23. A belt and sprocket assembly comprising:aplurality of identical linked modules of unitary constructioninterconnected in an end-to-end relation to form a belt, each moduleincluding: a plurality of link members of identical shape; each memberhaving a flatted elliptical portion with first and second ends and atooth portion projecting outward from said elliptical portion; said endseach having first and second pivot holes therethrough and defining firstand second pivot axes axially through said pivot holes; a plurality ofintermediate rigid members integral with said link members for spacingsaid plurality of link members equally one from the other to coaxiallyalign first and second pivot axes of respective link members and provideinterpositioning of the first link member ends of one link module withinspaces between second link member end of an adjacent link module; saidfirst and second pivot axes defining a pitch plane and said tooth ofeach link member being symmetrically disposed about a plane orthogonalto the pitch plane and parallel to and bisecting the pitch axes; meansextending through said pivot holes of said link member ends to secureadjacent modules one to the other and provide for pivotable rotation ofadjacent link modules; said projecting tooth of each module having firstand second working surfaces each symmetrically disposed on a respectiveside of said orthogonal plane; said surfaces intersecting at a lineparallel to the pivot axes in said orthogonal plane; each workingsurface having a shape in the range between a cylindrical segment and achord of a cylindrical segment having a center located .[.at thefarthest pivot axis or.]. between .[.that.]..Iadd.the farthest pivot.Iaddend.axis and the orthogonal plane; said module including a singletapered side which tapers toward the projecting tooth such that incross-section the module is narrower near the tooth, the taper having anangular configuration to mate with a corresponding V-shaped sprocketwheel; said module pivotably connected at respective first and secondlink ends, the tapered side of each module being opposite the taperedside of adjacent modules to provide an average cross-section of saidbelt having a V-shaped configuration to mate with a correspondingV-shaped wheel; a V-shaped tooth sprocket wheel having recesses betweenadjacent teeth thereof, each of said recesses including a pair of facingsurfaces of shape corresponding to the pair of working surfaces of saidprojecting tooth; only the teeth of said link members of respectivemodules being in driving engagement with the recesses of said sprocketwheel, the engaged link belt and sprocket wheel exhibiting minimalscrubbing action and chordal action and; said teeth of said sprocketwheel engaging said link modules and being radially aligned withrespective pivot axes during sprocket wheel and link module engagement.24. The assembly of claim 23 wherein said tooth is blunted adjacent saidline of intersection by a surface formed by a cylindrical segment havingits axis on said line.
 25. The assembly of claim 23 wherein said toothis truncated adjacent said line of intersection.
 26. The assembly ofclaim 23 wherein said link ends and tooth are of the same width.
 27. Theassembly of claim 23 wherein the projecting teeth of adjacent linkmembers are joined with material of cross-section identical to the toothmember to form a solid tooth member extending the width of the linkmodule.
 28. A linked belt and sprocket assembly comprising:a pluralityof identical linked modules interconnected in end-to-end relation toform a belt, each module having one or more links of the same length andwidth and sufficiently rigid to resist bending in the plane of anassociated sprocket wheel, each link having first and second ends, eachlink end having a pivotal hole defining first and second pivotal axes;said link ends having no driving engagement with an associated sprocketwheel; each of said modules having at least one driving tooth integralwith and protruding thereform substantially normal to the pitch linebetween said pivotal axes and intermediate the latter; said tooth havinga pair of working surfaces, each of the working surfaces having a shapein the range between and including that of a cylindrical segment and achord of said segment; the .[.axis.]. .Iadd.axes .Iaddend.of .[.each.]..Iadd.the .Iaddend.working .[.surface.]. .Iadd.surfaces .Iaddend.being.Iadd.spaced apart and .Iaddend.parallel with the pivotal axes of thelink and positioned intermediate the pivotal axes .[.or coincident withthe pivotal axis furthest from that surface.].; the pair of workingsurfaces being part of a pair of intersecting loci; the shape of each ofthe working surfaces being such that the tangent angle of each suchsurface is not more than 90°; one of said pluralities of link ends ofeach said a module being engaged between one of said pluralities of linkends of an adjacent module except for the individual link endspositioned at the extreme sides of said belt; means extending throughsaid holes pivotally connecting said modules at engaged link ends; atoothed sprocket wheel having recesses between adjacent teeth thereof,each of said recesses including a pair of facing surfaces of shapecorresponding to the pair of working surfaces of said driving tooth; andonly the teeth of said connected links being in driving engagement withthe recesses of said sprocket wheel, the engaged linked belt andsprocket wheel exhibiting minimal scrubbing action and chordal action.29. A linked belt assembly as defined in claim 1 wherein said modulesare each of integral construction.
 30. A linked belt assembly as definedin claim 29 wherein said modules each include:intermediate membersintegral with and joining the links to preserve the parallel relation ofsaid link ends and said axes.
 31. A linked belt assembly as defined inclaim 1 wherein the links of said module are of solid material along theaxis of driving force. .Iadd.
 32. A belt and sprocket assemblycomprising a plurality of linked end-to-end modules of unitaryconstruction connected in end-to-end relation to form a belt drivingsystem, each module including:a plurality of rigid link ends defined bythe modules at opposite ends of the module for linking modulesend-to-end, said link ends at opposite ends defining first and secondpivot holes along a set of parallel axes extending through the holes, anintermediate rigid member integral with said link ends in each beltmodule presenting opposed surfaces comprising a load bearing surface anda driving tooth with a driving tooth surface extending from a surfaceopposite to the load bearing surface disposed substantially parallel tothe load bearing surface, said rigid member supporting said link ends todispose the link ends along the respective axes and permitinterpositioning of the first link ends of one module within spacesbetween second link ends of an adjacent end-to-end module, said drivingtooth disposed in a plane substantially orthogonal to the pivot holeaxes, means extending through the respective first and second pivotholes of adjacent end-to-end modules to secure modules to each other forrelative pivotable rotation of adjacent end-to-end modules, saidprojecting tooth having at least one working surface disposed forengaging a mating said sprocket assembly in a belt driving relationship,said working surface having a shape in the range between a cylindricalsegment and a chord thereof with a center located in a plane coplanarwith the axes through the pivot holes between the most remote pivot axisand a midpoint between the pivot holes, and the shape of the workingsurface being such that the tangent angle is not more than 90 degrees,and a mating sprocket wheel in said sprocket assembly definingconsecutive recess surfaces for mating in driving relation with teethdriving surfaces on said at least one working surface for exhibitingminimal scrubbing action. .Iaddend. .Iadd.
 33. The belt driving systemof claim 32 further comprising:two said working surfaces on said drivingtooth having respective contour shapes symmetrically disposed about atooth plane parallel to the first and second pivot axes, said contourshapes meeting in an apex substantially coincident with the tooth plane..Iaddend. .Iadd.34. The belt driving system of claim 33 furthercomprising a tooth with the contoured shapes truncated for presenting atooth surface substantially parallel to the load bearing surface..Iaddend. .Iadd.35. A module for constructing hinged, linked, endlessbelt structures formed of substantially similar end-to-end connectedmodules and driven by a sprocket wheel, comprising in combination;afirst plurality of spaced apart link ends of substantially the samewidth, each link end of said first plurality being formed tocircumscribe a pivotal hole, the holes of said first plurality beingarranged for coaxial alignment along a first pivotal axis, a secondplurality of spaced apart link ends of substantially the same width,each link end of said second plurality being formed to circumscribe apivotal hole, said holes of said second plurality being arranged forcoaxial alignment along a second pivotal axis parallel to said firstaxis, an intermediate portion integrally formed with and joining saidfirst and second plurality of link ends so as to preserve the parallelrelationship of said axes and to form a substantially planar loadbearing surface for said belt, a driving tooth formed integrally withand protruding from said intermediate portion substantially normal tothe pitch line between said first and second axes and disposedintermediate the axes, said tooth having at least one working surfacewith a shape in the range between a cylindrical segment and a chord ofsaid segment, said shape being disposed about an axis of saidcylindrical segment, the axis of said working surface being parallelwith the pivotal axes of the link and positioned in a range intermediatethe midpoint between the pivotal axes and the pivotal axis furthest fromthat surface, each of aid plurality of link ends of said module beingpivotally engagable to intermesh with link ends of similar adjacentend-to-end modules, and the shape of the working surface being such thatthe tangent angle is not more than 90 degrees, and having an angularconfiguration sloping toward one of said axes of mating with acorresponding sprocket wheel drive surface to exhibit minimal scrubbingaction. .Iaddend.
 36. The module defined in claim 35 furthercomprising:two symmetrical driving surfaces with a curvature defining anapex, said driving tooth having a truncated surface substantiallyparallel with said load bearing surface.
 37. The module defined in claim35 further comprising:a tooth surface for said driving toothsymmetrically disposed on a respective side of a plane orthogonallydisposed to a pitch plane parallel to and bisecting said pivotal axes.